First off, I assume you're addressing this to me because I helped you to solve what would appear now to be a related problem in [https://support.mozilla.org/questions/1492345 another thread], but that's not really a good idea because, by doing so, you may be inhibiting from replying others who might know better than me how to solve your problem. In particular, if your problem requires OS specific troubleshooting, I may not be able to help if I don't use the same OS that you do (I use Mac OS, not Windows or Linux). So it's usually better to not address your question to anyone in particular. That said, start Thunderbird in <b>Troubleshoot Mode</b>. The following article explains how to do that and why it can be useful to help identify the cause of a problem: https://support.mozilla.org/kb/troubleshoot-mode-thunderbird What's your operating system? If Windows, start in <b>Safe Mode with Networking</b> mode. You may have to connect your computer to the router with an Ethernet cable, WiFi is disabled in Safe Mode: https://support.microsoft.com/help/12376/windows-10-start-your-pc-in-safe-mode Does any of that make the problem go away?